Merge (SQL)
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A relational database management system uses SQL MERGE (aka. upsert) statements to INSERT new records or UPDATE existing records depending on whether or not a condition matches. It was officially introduced in the SQL:2003 standard.
The usage is as follows:
- MERGE INTO table_name USING table_name ON (condition)
- WHEN MATCHED THEN UPDATE SET column1 = value1 [, column2 = value2 ...]
- WHEN NOT MATCHED THEN INSERT (column1 [, column2 ...]) VALUES (value1 [, value2 ...])
Other non-standard implementations
Some other database management systems support this, or very similar behavior, through their own, non-standard SQL extensions.
MySQL, for example, supports the use of INSERT ... ON DUPLICATE KEY UPDATE syntax[1] which can be used to achieve the same effect. It also supports REPLACE INTO... syntax[2], which has a similar (although subtly different) effect.